UROCOPTIS, S. G. GONGYLOSTOMA. 183 



This group comprises a great variety of shell-forms, from 

 short and swollen to long and fusiform ; the last whorl being 

 either adnate to the preceding or projected in a long neck. 

 The subgenus is characteristic'of western Cuba, as Idiostemma 

 is of eastern; only a few forms occurring in the east. Up to 

 this time very few are known from central Cuba, east of 

 Matanzas province. Gongylostoma is chiefly developed upon 

 and near the Sierra de los Organos, including the lower con- 

 tinuation of the same mountain system eastward to Matanzas. 

 To what extent they follow the hill country still further to 

 the east remains to be determined; but Pinar del Rio appa- 

 rently has the greatest variety of forms, as well as the largest 

 number of species. 



The subgenus was subdivided in my paper of 1898 accord- 

 ing to the number of spiral axial lamellae above the dentate 

 basal one; but further study shows this to be in many cases 

 a secondary character, even coloration and sculpture-pattern 

 outranking it. There are many phyla in the group, more or 

 less exactly parallel or homoplastic in internal structure, and 

 so far as I can see, inter-related about as indicated in the 

 accompanying diagram, in which the "concreta group" may 

 perhaps represent primitive forms, since it is likely that the 

 whole series arose from a stock in which there was one spiral 

 axial lamella with a lower cord above it. 



3 or more f Calloni ^ Pycnoptychia 



axial 

 lamellae . 



i 



f Esochara 

 2 axial 



iocallonia 



Paracallonia 



Sectilumen 

 I 



trilamellata gr. 





lamellae. Elegans group coerulans group pruinosa gr. 



| | ventricosa gr. 



1 lamella. -{ Tetrentodon concreta gr. torquata gr. wrighti gr. 



No lamellae { Cochlodinella 



Diagram showing approximate relationships of West Cuban 

 groups of Urocoptis. 



The group of U. elegans is a middle point whence variously 

 modified phyla radiate, the group of U. cczrulans another. 

 The comparative lengths of some lines in the diagram are 



